Timepiece having a circuit adapted to electrically sustain amplitude-regulated oscillation of a resonator



July 22, 1969 l K ADLER 3,457,524

TIMEPIECE HAVING A CIR'JUIi ADAPTED TO ELECTRICALLY SUSTAIN I AMPLITUDE-REGULATED OSCILLATION OF A RESONATOR -Filed July 13, 1967 lll lll INVENTOR KARL AD ER B: r

A ORN United States Patent US. Cl. 331-116 3 Claims ABSTRACT OF THE DISCLOSURE An electric timepiece having a resonator, such as a balance wheel, a transistor, coils and regulating means for sustaining oscillation of the resonator at a constant amplitude, and means for preadjustment of the desired resonator amplitude without alfecting the regulating characteristics.

This invention relates to an electric timepiece having a control coil and driving coil, such coils being connected into the input circuit and output circuit respectively of a transistor thereby forming a feed-back circuit together with the transistor and a voltage source for sustaining the oscillation of a mechanical oscillating system or resonator.

In timepieces of this type, particularly when used in watches, the voltage source should be utilized as completely as possible but high time-keeeping accuracy of the timepiece is required until the source is completely used.

For this purpose it has already been known to connect the driving coil between the emitter of the transistor and the one terminal of the voltage source, to connect the control coil between the emitter and the base of the transistor, and to connect a diode between the base and the said one terminal of the voltage source. This circuit has the purpose to maintain a constant voltage at the driving coil and consequently a constant current in the driving coil independently of the voltage of the source. However, the regulating characteristics of this circuit depend on the characteristics of the transistor and of the diode as used so that this prior circuit does not allow adjustment of the desired amplitude of the resonator, for instance a balance wheel without further adjustable elements.

In another prior circuit a voltage divider is provided in the emitter circuit of the transistor, the diode being connecteed to the tapping of the voltage divider. Particularly, a driving coil having a tapping was used and the diode was connected to this tapping. It is obvious that in this circuit no adjustment of the resonator amplitude is possible and that the voltage and current is not properly regulated in one branch of the driving coil. Experiments have shown that no stability of the resonator amplitude, particularly of a balance-wheel amplitude is obtained with this circuit and that, therefore, considerable deviations from proper time-keeping occur depending on the voltage of the source.

In another similar prior circuit, a voltage divider with one or two regulating diodes is connected between the emitter circuit comprising the driving coil and the collector circuit, whereby the control coil is connected between the tapping of the voltage divider and the base of the transistor. In this case a variable resistor is connected between the tapping of the voltage divider and the collector of the transistor by which the rest potential at the tapping and at the base of the transistor and consequently the desired amplitude may be adjusted. However, this circuit bascially differs from the idea of effecting a direct regulating by connection of the regulating diode to the base of the transistor, whereby a less efiicient regulation results. Further, it is impossible to select a desired amplitude by adjustment of said variable resistor without at the same time affecting the regulating characteristics, because any change of the rest potential at the base of the transistor and at the tapping of the voltage divider respectively also changes the operating point of the diode or diodes.

This invention aims in providing means in a circuit of the first-mentioned type having good regulating characteristics at variable voltage of the source, for adjusting the desired amplitude of the resonator without affecting the regulating characteristics. This result may be obtained in a very simple manner by providing a variable resistor series-connected with said control coil between the base and emitter of the transistor. In combination with the particular regulating circuit it is possible within wide limits to adjust the current flow in the control coil and the braking action of such currents flowing in the control coil, whereby the resonator amplitude may properly be adjusted by adjustment of the control current. Although the total resistance of the control circuit is changed in relatively wide limits, the control circuit may still be considered as being high-ohmic compared with the regulating circuit which is very low-ohmic, particularly when Zener diodes are used, so that by the adjustment of the resistor and of the current in the control circuit the amplitude regulation is practically not afiected.

One embodiment of the invention will now be described by way of example and with reference to the accompanying drawing.

The timepiece illustrated in the drawing has a driving coil 1 and a control coil 2 preferably wound upon each other in a common plane and adapted to swing through a magnetic field of small dimensions in circumferential direction. Coils 1 and 2 are mounted to control a balance wheel 7 as schematically indicated in the drawing. For the zero position or neutral position of the balance wheel coils 1 and 2 mounted on the same are symmetrically positioned in the magnetic field. The driving coil 1 is connected between the positive terminal of a voltage source 3 and the emitter of a pup-transistor 4. The control coil 2 with a series resistor 5 is connected between the emitter and the base of transistor 4. A Zener diode 6 is connected between the positive terminal of the voltage source and the base of the transistor 4. The breakdown voltage of the Zener diode is substantially lower than the voltage of the source 3 in its new condition.

Operation of this timepiece is as follows:

In the rest condition or when the coils 1 and 2 are outside the magnetic field when the balance wheel oscillates, no voltage is induced in the control coil and the whole circuit is practically without current. The base of transistor 4 is maintained at emitter potential through the coil 2 and the resistor 5 so that the transistor is practically cut oif. Practically no current flows in the Zener diode 6 because the base is practically maintained at the potential of the positive terminal of the voltage source.

When the coil 2 produces a positive pulse at the base during its passage through the magnetic field in the one direction, the condition of the circuit remains practically unchanged because the diode 6 and the transistor 4 remain cut off. When the control coil 2 swings in the other direction, a neegative voltage pulse appears at the base of the transistor whereby the transistor becomes conductingfBy the pulse of driving current thereby flowing in the driving coil 1 a voltage drop occurs this coil so that the emitter voltage decreases. This voltage drop is transmitted through the resistor 5 and the coil 2 to the base so that practically no negative feed-back occurs by the connection of the driving coil or load into the emitter circuit. The common voltage drop at the emitter and at the base of the transistor relatively to the positive terminal of the voltage source is limited to a practically constant value by the Zener diode 6 which becomes conducting when a predetermined voltage at the base is reached and prevents a further decrease of the base voltage. From the relatively high-ohmic design of the control circuit with the resistor 5 a relatively loose coupling between the emitter 'andthe base of the transistor results so that the base voltage is determined by the practically constant Operating voltage of the Zener diode when the same is conducting. Thereby, an automatic regulation of the operating voltage at the driving coil 1 is obtained because the current and consequently the voltage drop in coil 1 is automatically regulated to a value for which the emitter is maintained at a potential slightly above the regulated base potential.

The regulating circuit is very efficient because the Zener diode having a very low dynamic internal resistance in its operating range regulates the base circuit which is relatively high-ohmic independently of the adjustment of resistor 5. In other words the regulating efiect of the Zener diode 6 is practically independent of the total resistance of the control circuit (2, 5) and of the control current flowing therein, that is, the base voltage is maintained at a predetermined potential relatively to the positive terminal of the voltage source independently of the control current in coil 2 when the transistor is conducting, whereby the voltage at the driving'coil and the current in the same are also maintained at a constant value. However, the current in the control circuit depending on the adjustment of resistor 5 produces a braking effect depending on the current flow during induction'of a current pulse. It is thus possible to adjust the resonator. amplitude by adjustment of resistor 5 without thereby affecting the above voltage regulation by the Zener diode 6.

A practical embodiment of the circuit had the following elements and values:

Voltage of source 3 v .5 to 3 Number of turns, coil 1 500 Number of turns, coil 2 2,800 Resistor 5 10kt) Diode 6 BZY83D1 Transistor 4 Of course, -other;values and elements, particularly of the operating voltage of the diode 6 may be used,-under the conditionthat this operating voltage is below the voltage of the source 3 for the whole lifetime of the source. A npn-transistor may be used whereby the driving coil 1 has to be connected to the emitter and the diode 6 is to be connected in proper polarity between the base and the negative terminal of the source 3.

Another suitable alinear element may be used instead of a Zener diode, for instance a diode having a Zener characteristic but operating in forward direction.

What is claimed:

1. An electric timepiece having a control coil and driving coil, such coils being connected into the input circuit and output circuit respectively of a transistor thereby forming a feed back circuit together with the transistor and a voltage source for sustaining the oscillation of a mechanical oscillating resonator, the driving coil being connected between the emitter of the transistor and the one terminal of the voltage source and the control coil being connected between the emitter and the base of the transistor, while a diode is connected between the base of the transistor and the said one terminal of the voltage source, and a variable resistor series-connected with said control coil between the base and emitter of the transistor.

2. A timepiece according to claim 1, wherein the said diode is a Zener-diode.

3. A timepiece according to claim 2, wherein the value of said variable resistor exceeds the dynamic internal resistance of the Zener diode.

References Cited UNITED STATES PATENTS 3,100,278 8/1963 Reich 331-116 JOHN KOMINSKI, Primary Examiner U.S. Cl. X.R. 

